1. Field of the Invention
The present invention relates to a method of beveling a plate-like metal member.
2. Description of the Related Art
Plate-like metal members to be beveled include elements of a belt for use in continuously variable transmissions, for example. As shown in FIG. 5 of the accompanying drawings, an element 1 of such a transmission belt comprises a body 2 for contacting a pulley of a continuously variable transmission (not shown), and a head 4 joined to the body 2 by a narrow neck 3. The element 1 is blanked out of a metal plate (not shown). The body 2 has a pair of symmetrical saddles 5, and the head 4 has a pair of ears 6 spaced respectively, from the saddles 5 with gaps therebetween. The element 1 includes undercuts 3d defined at upper and lower ends of the neck 3. A pair of laminated rings 8 each comprising a stack of metal sheet rings 7 is held in engagement with the respective saddles 5. Although not shown, the transmission belt comprises an annular array of stacked elements 1 that are held together in an annular shape by the laminated rings 8.
If the neck 3 of the element 1 has sharp edge corners 3a or is burred at edge corners 3a when the element 1 is blanked, then the metal sheet rings 7 tend to be damaged by contact with the neck 3. To avoid such damage, it has been customary to deburr and bevel the edge corners 3a of the neck 3.
It is known in the art that, as shown in FIG. 6 of the accompanying drawings, a rotating grinding belt 60 is held in sliding contact with the edge corners 3a of the neck 3 of the element 1 to deburr and bevel the edge corners 3a of the neck 3.
According to the known process, each element 1 is supported on a rotary disk 61, and rotated thereby while the edge corners 3a of the neck 3 are being held against the grinding belt 60. As shown in FIG. 7(a) of the accompanying drawings, the grinding belt 60 passes between an upper edge 5a of one of the saddles 5 and a lower edge 6a of the corresponding ear 6 into abutment against the neck 3. Therefore, the width of the grinding belt 60 is of such dimension that it can pass between the upper edge 5a of the saddle 5 and the lower edge 6a of the ear 6.
However, if the upper edge 5a of the saddle 5 is slightly arcuate in shape, then the distance e between the crest of the upper edge 5a of the saddle 5 and the lower edge 6a of the ear 6 is relatively small, and a range f of the neck 3 which is beveled by the grinding belt 60 having passed through the distance e is smaller than a range g of the neck 3 which is held in contact with the metal sheet rings 7 of the laminated ring 8. Specifically, the rings 7 of the laminated ring 8 engaging the saddle 5 slide along an extension h (see FIGS. 7(a) and 7(b)) of the upper edge 5a of the saddle 5 into abutting engagement with the neck 3, as shown in FIG. 7(b) of the accompanying drawings. At this time, a lower one of the rings 7 abuts against a range i outside of the beveled range f. Therefore, the conventional beveling process using the grinding belt 60 fails to bevel the entire range g of the neck 3 which is contacted by the laminated ring 8. As a result, the rings 7 are not fully protected against damage because they tend to contact the range i of the neck 3 where burrs and sharp edge corners remain unremoved.
According to the conventional beveling process using the grinding belt 60, furthermore, as shown in FIG. 6, the elements 1 supported on the rotary disk 61 are beveled one by one. Consequently, a large number of elements 1 are beveled with poor efficiency in a prolonged period of time.
It is therefore an object of the present invention to provide a method of beveling a plate-like metal member at a predetermined position thereof reliably and efficiently.
According to the present invention, there is provided a method of beveling a blanked plate-like metal member having an recess including an undercut therein, comprising the step of ejecting a stream of a liquid mixed with particle members toward an edge to be beveled of the recess thereby to bevel the recess.
When the stream of the liquid mixed with particle members is ejected toward the edge to be beveled of the recess including the undercut, the particle members collide with the edge to be beveled, polishing, removing burrs from, and beveling the edge of the recess.
The particle members have such directivity that they collide accurately with the recess in the plate-like metal member. Therefore, the recess can reliably be beveled even if it is located in a relatively narrow region. When the particle members collide with the edge to be beveled, they impart a residual stress in the edge, thereby increasing the mechanical strength of the edge.
The plate-like metal member may comprise an element of a belt for use in a continuously variable transmission. A plurality of such elements are stacked in an annular form and held together by sheet rings, providing the transmission belt. The element comprises a body for contacting a pulley of the continuously variable transmission, and a head joined to the body by a narrow neck, the body having a saddle engageable by the sheet rings, the head having an ear spaced from the saddle with a gap therebetween. The recess is defined by an upper edge of the saddle, a side edge of the neck, and a lower edge of the ear. The stream is ejected toward the edge to be beveled which extends in a range between a point of intersection between the side edge of the neck and an extension of the lower edge of the ear and a point of intersection between the side edge of the neck and an extension of the upper edge of the saddle.
Since the particle members are ejected with directivity, they can collide accurately with a point of intersection between the side edge of the neck and the extension of the upper edge of the saddle. The particle members can therefore reliably deburr and bevel the edge to be beveled which extends in the range between the point of intersection between the side edge of the neck and the extension of the lower edge of the ear and the point of intersection between the side edge of the neck and the extension of the upper edge of the saddle, which range would be contacted by the sheet rings on the side edge of the neck. Therefore, the sheet rings are reliably prevented from damage by contact with the neck. Furthermore, because the mechanical strength of the neck is increased by the residual stress that has been developed in the neck by the impinging particle members, the neck is further protected against damage by contact with the neck.
After the edge is deburred thereby to bevel the recess, the recess is finished by removing a bulge formed on an outer surface of the edge by deburring the edge. Therefore, the recess is given a highly accurate beveled shape. The recess may be finished by barrel polishing.
A stack of the plate-like metal members may be moved in a direction along the stack while recesses in the plate-like metal members are being exposed to one side, and the stream may be ejected toward edges to be beveled of the recesses thereby to bevel the recesses. Therefore, many plate-like metal members can be beveled simultaneously with increased efficiency. If the plate-like metal members comprise elements of a belt for use in a continuously variable transmission, then the stack of elements may be moved in a direction of the stack, and the stream may be ejected toward edges to be beveled of the recesses thereby to bevel the recesses. Consequently, may elements can be beveled simultaneously with increased efficiency.
At this time, the stream may be ejected toward edges to be beveled on one diagonal line of the neck of a stack of the elements to bevel the edges while moving the stack of elements in a direction along the stack, then the stack of elements may be turned 180xc2x0 about an axis along the direction, and the stream may be ejected toward edges to be beveled on the other diagonal line of the neck of the stack of the elements to bevel the edges while moving the stack of elements in the direction along the stack. In this fashion, the four edge corners of a pair of recesses defined in each element can efficiently be beveled.
The particle members may be made of a material selected from the group consisting of glass, alumina, steel, cast iron powder, and zirconia. The particle members made of the above material are mixed with the liquid, and the stream of the liquid is ejected to the edge to be beveled. Since the particle members collide accurately with the edge to be beveled because of the directivity they have, the edge can be beveled well.
The particle members may be crushed upon collision with the edge to be beveled. The particle member that can be crushed upon collision with the edge to be beveled may comprise glass beads. The glass beads are broken by the impact at the time they collide with the edge. The fragments of the glass beads thus broken are pressed again against the edge by the stream of the liquid for reliably and efficiently beveling the edge.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate a preferred embodiment of the present invention by way of example.